Electronics - Parallel Circuits - Discussion
Discussion Forum : Parallel Circuits - General Questions (Q.No. 20)
20.
What are the individual values of two parallel resistors whose RT is 8 ohms, when one has double the resistance of the other?
Discussion:
15 comments Page 1 of 2.
Paul said:
6 years ago
Remember, the total Resistance for a Parallel Network is always lesser than the smallest value of the resistance in the network.
Then just reverse Engineer the values from options C & D, applying the product over sum since there are only two resistors in the network to get the total Resistance.
For C (8 & 10).
R = (8*10)/(8+10) = 4.444.
for D (12 & 24),
R = (12*24)/(12+24) = 8.
Option D, has R total of 8 ohms, so the answer is correct, D.
Then just reverse Engineer the values from options C & D, applying the product over sum since there are only two resistors in the network to get the total Resistance.
For C (8 & 10).
R = (8*10)/(8+10) = 4.444.
for D (12 & 24),
R = (12*24)/(12+24) = 8.
Option D, has R total of 8 ohms, so the answer is correct, D.
Pre said:
9 years ago
As per condition given r1 = 2r2.
R total = r1*r2/r1 + r2.
=> 2r1 * r1/3r1 (r1 and r1 get cancelled).
Then,
=> 2r1/3 = R total = 8.
Then,
r1 = 8 * 3/2,
=> 4 * 3,
=> 12.
Then, r2 = 24.
So the answer is D.
R total = r1*r2/r1 + r2.
=> 2r1 * r1/3r1 (r1 and r1 get cancelled).
Then,
=> 2r1/3 = R total = 8.
Then,
r1 = 8 * 3/2,
=> 4 * 3,
=> 12.
Then, r2 = 24.
So the answer is D.
Sreeyush Sudhakaran said:
1 decade ago
RT=R1R2/R1+R2
Given RT=8 Ohms Let R1=R then R2 = 2R
8= RX2R/R+2R
8 = 2R^2/3R
8 = (2/3)XR
R = 24/2 =12 Ohms R1=12 ohms and R2=2R=2x12= 24 Ohms
Given RT=8 Ohms Let R1=R then R2 = 2R
8= RX2R/R+2R
8 = 2R^2/3R
8 = (2/3)XR
R = 24/2 =12 Ohms R1=12 ohms and R2=2R=2x12= 24 Ohms
Mani said:
7 years ago
Given R total=8ohms,
Condition R1=r,
R2=2r.
R1&R2 are connected in parallel,
R total=R1*R2/R1+R2,
8=r*2r/r+2r,
r=12,
R1=r=12,
R2=2r=2*12=24.
Condition R1=r,
R2=2r.
R1&R2 are connected in parallel,
R total=R1*R2/R1+R2,
8=r*2r/r+2r,
r=12,
R1=r=12,
R2=2r=2*12=24.
(1)
Birundha said:
1 decade ago
R1+R2/R1R2=8
heraR1=2R2
3R2/2R2^2=8
1.5/R2=8
8R2=1.5
R2=1.5/8
R2=.18
R1=.375
please check in this type and tell clear ans for me.
heraR1=2R2
3R2/2R2^2=8
1.5/R2=8
8R2=1.5
R2=1.5/8
R2=.18
R1=.375
please check in this type and tell clear ans for me.
Karthik said:
1 decade ago
I am Not agree that
Correct answer is
if R1,R2-16Ohms so that only RT =8Ohms
So Given option is wrong
Pls clarify...
Correct answer is
if R1,R2-16Ohms so that only RT =8Ohms
So Given option is wrong
Pls clarify...
Prasanna said:
1 decade ago
@Burunda you are wrong.
1/Rt = 1/R1 + 1/R2.
But you have written Rt = 1/R1+1/R2 which is giving you wrong answer.
1/Rt = 1/R1 + 1/R2.
But you have written Rt = 1/R1+1/R2 which is giving you wrong answer.
Chinnu said:
1 decade ago
Gn:Rt=8
also r1||r2;nd r1=2r2 =>r1/2=r2
=>(r1*r1/2)/(r1+r1/2)=8
=>r1=24
r2=r1/2 =>r2=12
also r1||r2;nd r1=2r2 =>r1/2=r2
=>(r1*r1/2)/(r1+r1/2)=8
=>r1=24
r2=r1/2 =>r2=12
Umair said:
4 years ago
@Jessi.
If there are three and the same condition is given then how can you define?
If there are three and the same condition is given then how can you define?
Mamatha said:
1 decade ago
Let R1 be x, so R2 is 2x
8=(x*2x)/(x+2x)
So x is 12
Hence R1 is 12 and R2 is 24
8=(x*2x)/(x+2x)
So x is 12
Hence R1 is 12 and R2 is 24
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